This invention relates to roll forming metal and more particularly to a process for forming a multirow bearing race by roll forming and to a race and bearing formed thereby.
An antifriction bearing widely used in transportation equipment and elsewhere has a unitary outer race, two inner races, and tapered rollers arranged in two rows between the outer race and the two inner races, there being a separate row around each inner race. The unitary outer race, more commonly referred to as a double cup, has a pair of tapered raceways which are presented inwardly and taper downwardly to a cylindrical intervening surface or small inside diameter (SID), while the inner races or cones each have tapered raceways that are presented outwardly. Typically, the double cups are machined from tubing or forged rings, but owing to the taper of the raceways, the machining removes a considerable amount of metal. This makes the manufacture of double cups time-consuming and expensive.
To a lesser extent double cups are formed in a cold rolling operation, but this also requires a considerable amount of machining and stock removal. In this regard, the roll-forming begins with a cylindrical blank of plain rectangular section (PRS blank--FIG. 1). The roll forming produces a ring form having tapered raceways and the cylindrical intervening surface between those raceways. But to acquire the raceways and the intervening surface, the metal of the blank must be displaced outwardly beyond the ends of that surface, and this leaves the exterior surface of the ring form with a groove located immediately outwardly from cylindrical intervening surface. The groove in turn renders the ring form difficult to guide during subsequent grinding. As a consequence, the ring form is machined on its exterior to remove an amount of metal sufficient to eliminate the groove. This results in almost as much stock removal as does machining from a tube or forged ring.